Cavus and cavovarus are descriptive terms used to describe a foot in which the arch is higher than expected population norms. It is the opposite of pes planus, or flatfoot, which is a foot with little to no arch. A cavus foot, just like a flatfoot, can be problematic. However, the problems seen with high arch cavus feet are generally different, and in some ways, may be opposite of the problems seen with flat feet.
Severely cavus feet may not fit into shoes very well because of their shape. They can seemingly toe-in at times when walking. They may appear to have a humpback deformity with bossing on top of the foot that can become painful from shoe pressure where the laces tie.
A cavus foot is less flexible than a flatfoot. For this reason, during walking, cavus feet do not absorb shock as well as feet with lower arches. Due to this rigidity, a cavus type foot is more prone to arthritic changes particularly in the midfoot and hindfoot. These arthritic changes may cause the bone to remodel and grow spurs, which can exacerbate the painful bossing on top of the foot. The arthritic changes may also cause achiness in the arches and the midfoot after a long day of standing or walking. This lack of flexibility and shock absorption may also predispose to plantar fasciitis related heel pain (see section on plantar fasciitis).
Patients with cavus feet can also present with symptoms of lateral ankle instability (see section on ankle instability). Ankle instability is a diagnosis in which patients have recurrent ankle sprains, or the feeling that their ankle is unstable or will give way. The causes of ankle instability are variable but are generally based on foot shape and a lack of ligamentous and tendinous support. Patients with cavus feet tend to walk on the outer border of the sole, or the side of the foot. Based on laws of physics, walking on the outside of the foot renders these individuals more prone to roll the foot and ankle, and experience an ankle sprain. Severe ankle sprains can lead to permanent damage of the lateral ligaments and tendons, which leads to even more sprains or ankle instability.
In patients with cavus feet who don’t experience severe sprains or ankle instability, the peroneal tendons (see section on peroneal tendons), which serve to stabilize the ankle, may become overworked. As the patient walks on the outer border of the foot the peroneal tendons stabilize the foot to keep it from rolling and prevent sprains. This can lead to soreness or painful spasm of the tendons and sometimes even peroneal tendon tears. Often times, in order to repair and appropriately address peroneal tendon damage, the cavus shape of the foot must be addressed as well.
The surgical correction of a cavus foot may require multiple procedures to decrease the high arch to a more normal level. The descriptive term cavus foot includes a number of deformities ranging from the hindfoot (heel) to the forefoot (toes). To effectively flatten the arch, it may require a combination of osteotomies (cutting and shifting the bone) of the heel, midfoot, and forefoot. Sometimes tendons may be released or transferred as part of the correction to further balance out the foot. Cavus foot balancing may also be necessary in combination with surgery to adequately address other pathology such as ankle instability, peroneal tendon tears, and midfoot arthritis.
The recovery from surgical correction of a cavus foot is variable, but in general, a non-weight bearing period of 6-8 weeks is required. Usually the bone healing at the osteotomy site is the rate-limiting step. Around 6-8 weeks weight bearing in a boot is allowed and physical therapy is commenced. Transition into a standard shoe generally occurs around 12 weeks.
Copyright Protected. Jesse F. Doty MD. Foot and Ankle Specialist. Orthopaedic Surgery. Chattanooga, Tennessee.